<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="author" content="wangbo">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{margin: 0px;padding: 0px;}
    ul,li{list-style: none;}
    ul.room{display: none;}
    #room>li{float: left; }
    li>div,.room li{padding: 0 20px;border: 1px solid #ccc; }
    #room li:hover .room{     display: block;  }
  </style>
</head>
<body>
  <ul id="room">
    <li>
      <div>210</div>      
      <ul class="room">
        <li>赵云</li>
        <li>关羽</li>
        <li>张飞</li>
      </ul>
    </li>
    <li>
      <div>210</div>
      <ul class="room">
        <li>赵云</li>
        <li>关羽</li>
        <li>张飞</li>
      </ul>
    </li>
    <li>
      <div>210</div>
      <ul class="room">
        <li>赵云</li>
        <li>关羽</li>
        <li>张飞</li>
      </ul>
    </li>
  </ul>
</body>
</html>